Digital broadcasting system and method of processing data

ABSTRACT

A digital broadcasting system and method of processing data are disclosed. Herein, a method of processing data in a transmitting system includes creating a data group including a plurality of mobile service data packets, re-adjusting a relative position of at least one main service data packet of a main service data section, the main service data section including a plurality of main service data packets, and multiplexing the mobile service data of the data group and the main service data of the main service data section in burst units. Herein, a position of an audio data packet among the main service data packets of the main service data section may be re-adjusted. Also, a position of an audio data packet included in the main service data section may be re-adjusted based upon a multiplexing position of the main service data section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/229,579, filed on Sep. 9, 2011, currently pending, which is acontinuation of U.S. patent application Ser. No. 11/960,561, filed onDec. 19, 2007, now U.S. Pat. No. 8,040,920, which claims the benefit ofearlier filing date and right of priority to Korean Patent ApplicationNo. 10-2006-0130276, filed on Dec. 19, 2006, and also claims the benefitof U.S. Provisional Application Ser. No. 60/871,408, filed on Dec. 21,2006, the contents of which are all hereby incorporated by referenceherein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital broadcasting system, and moreparticularly, to a digital broadcasting system and a method ofprocessing data that can receive and transmit (or process) digitalbroadcast signals.

2. Discussion of the Related Art

The Vestigial Sideband (VSB) transmission method, which is adopted asthe standard for digital broadcasting in North America and the Republicof Korea, is a system using a single carrier method. Therefore, thereceiving performance of the receiving system may be deteriorated in apoor channel environment. Particularly, since resistance to changes inchannels and noise is more highly required when using portable and/ormobile broadcast receivers, the receiving performance may be even moredeteriorated when transmitting mobile service data by the VSBtransmission method.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a digital broadcastingsystem and a data processing method that substantially obviate one ormore problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a digital broadcastingsystem and a method of processing data that are highly resistant tochannel changes and noise.

Another object of the present invention is to provide a digitalbroadcasting system and a method of processing data that can enhance thereceiving performance of a receiving system by performing additionalencoding on mobile service data and by transmitting the processed datato the receiving system.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod of processing data in a transmitting system of a digitalbroadcasting system may include creating a data group including aplurality of mobile service data packets, re-adjusting a relativeposition of at least one main service data packet of a main service datasection, the main service data section including a plurality of mainservice data packets, and multiplexing the mobile service data of thedata group and the main service data of the main service data section inburst units. Herein, a position of an audio data packet among the mainservice data packets of the main service data section may bere-adjusted. Also, a position of an audio data packet included in themain service data section may be re-adjusted based upon a multiplexingposition of the main service data section.

In another aspect of the present invention, a service multiplexer in atransmitting system includes a main service multiplexer, a mobileservice multiplexer, and a multiplexer. The main service multiplexermultiplexes compression-encoded main service data and main ancillarydata. The mobile service multiplexer multiplexes compression-encodedmobile service data and mobile ancillary data. And, the multiplexermultiplexes output data of the main service multiplexer and output dataof the mobile service multiplexer, thereby outputting the multiplexeddata to at least one transmitter located in a remote site.

In a further aspect of the present invention, a transmitter of a digitalbroadcast transmitting system includes a demultiplexer, a packet jittermitigator, a pre-processor, and multiplexer. The demultiplexer receivesand demultiplexes multiplexed main service data and mobile service data.The packet jitter mitigator adjusts a position of at least one mainservice data packet included in a main service data section, the mainservice data packet being demultiplexed and outputted from thedemultiplexer. The pre-processor performs additional encoding on themobile service data being demultiplexed and outputted from thedemultiplexer, and creates a data group including a plurality of encodedmobile service data packets. And, the multiplexer multiplexes andoutputs, in burst units, the mobile service data of the data group beingoutputted from the pre-processor and the main service data of the mainservice data section being outputted from the packet jitter mitigator.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a block diagram showing a general structure of adigital broadcasting system according to an embodiment of the presentinvention;

FIG. 2 illustrates a block diagram showing an example of a servicemultiplexer of FIG. 1;

FIG. 3 illustrates a block diagram showing an example of a pre-processorof FIG. 2;

FIG. 4 illustrates a block diagram showing an example of a transmitterof FIG. 1;

FIG. 5( a) to FIG. 5( d) illustrate a process of realigning main servicedata according to an embodiment of the present invention; and

FIG. 6 illustrates a block diagram showing a structure of a digitalbroadcast receiving system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. In addition,although the terms used in the present invention are selected fromgenerally known and used terms, some of the terms mentioned in thedescription of the present invention have been selected by the applicantat his or her discretion, the detailed meanings of which are describedin relevant parts of the description herein. Furthermore, it is requiredthat the present invention is understood, not simply by the actual termsused but by the meaning of each term lying within.

In the present invention, the mobile service data may either consist ofdata including information such as program execution files, stockinformation, weather forecast, and so on, or consist of audio/video(A/V) data. Additionally, the known data refer to data already knownbased upon a pre-determined agreement between the transmitter and thereceiver. Furthermore, the main service data consist of data that can bereceived from the conventional receiving system, wherein the mainservice data include A/V data. Also, a data service using the mobileservice data may include weather forecast services, traffic informationservices, stock information services, viewer participation quizprograms, real-time polls & surveys, interactive education broadcastprograms, gaming services, services providing information on synopsis,character, background music, and filming sites of soap operas or series,services providing information on past match scores and player profilesand achievements, and services providing information on productinformation and programs classified by service, medium, time, and themeenabling purchase orders to be processed. Herein, the present inventionis not limited only to the services mentioned above.

The present invention relates to a transmission system that can becompatible with the conventional transmission method. Additionally, thetransmission system may also multiplex the main service data and mobileservice data of the same channel, and then, transmit the multiplexeddata. When using the transmitting system according to the presentinvention, the mobile service data may be received while the user is ina mobile state (i.e., traveling). Also, the mobile service data may bereceived with stability despite the noise and diverse distortionoccurring in the channel.

Furthermore, the transmitting system according to the present inventionmay perform additional encoding, and insert data pre-known by bothtransmitting and receiving systems (i.e., known data) and transmit theprocessed data, thereby enhancing the receiving performance. The presentinvention may also mitigate packet jitter when multiplexing the mainservice data and the mobile service data.

FIG. 1 illustrates a block diagram showing a general structure of atransmitting system according to an embodiment of the present invention.Herein, the transmitting system includes a service multiplexer 110 and atransmitter 120. Herein, the service multiplexer 110 is located in thestudio of each broadcast station, and the transmitter 120 is located ina specific predetermined site. The transmitter 120 may be located in aplurality of different locations. Also, the plurality of transmittersmay share the same frequency. And, in this case, the plurality oftransmitters transmits the same signal. Accordingly, in the receivingsystem 130, a channel equalizer may compensate signal distortion, whichis caused by a reflected wave, so as to recover the original signal. Avariety of methods may be used for data communication each of thetransmitters 120, which are located in remote positions, and the servicemultiplexer 110. For example, an interface standard such as asynchronous serial interface for transport of MPEG-2 data (SMPTE-310M).

FIG. 2 illustrates a block diagram of a service multiplexer according toan embodiment of the present invention. Referring to FIG. 2, the servicemultiplexer includes a main service multiplexer 230 for multiplexing andoutputting main service data, a mobile service multiplexer 260 formultiplexing and outputting mobile service data, and a multiplexer 270for multiplexing and outputting the service data from both servicemultiplexers 230 and 260. More specifically, the main service data areencoded and compressed by a main A/V system 210, which are then outputto the main service multiplexer 230. Herein, if there is a plurality ofmain service data types, a plurality of main A/V systems may beprovided. The main service multiplexer 230 multiplexes the output of themain A/V system 210 and main ancillary/control data 220 and, then,outputs the multiplexed data to the multiplexer 270.

Similarly, the mobile service data are encoded and compressed by amobile A/V system 240, which are then output to the mobile servicemultiplexer 260. Herein, if there is a plurality of mobile service datatypes, a plurality of mobile A/V systems may be provided. The mobileservice multiplexer 260 multiplexes the output of the mobile A/V system240 and mobile ancillary/control data 250 and, then, outputs themultiplexed data to the multiplexer 270.

The multiplexer 270 multiplexes the output of the main servicemultiplexer 230 and the output of the mobile service multiplexer 260and, then, outputs the multiplexed data to at least one of thetransmitters. The output data of the multiplexer 270 is configured tohave a MPEG-2 transport stream (TS) format. At this point, if theservice data being transmitted to the transmitter 120 from the servicemultiplexer 110, are configured only of the main service data, theservice multiplexer 110 transmits the main service data to thetransmitter 120 at a data rate of approximately 19.39 Mbps.

However, when the service multiplexer 110 multiplexes the main servicedata and the mobile service data and outputs the multiplexed data to thetransmitter 120, the service multiplexer 110 transmits the main servicedata at a data rate lower than 19.39 Mbps. This applies more to themobile service data, since additional error correction encoding isperformed by the transmitter 120, thereby reducing the data rate.Therefore, the output data rate of the multiplexer 270 included in theservice multiplexer 110, which multiplexes and outputs main service dataand mobile service data, is always equal to or less than 19.39 Mbps.

If the output of the service multiplexer 110 is required to bemaintained at a constant data rate (e.g., at 19.39 Mbps), null data ornull data packet are/is inserted in at least one of the main servicemultiplexer 230, the mobile service multiplexer 260, and the multiplexer270, thereby setting the data rate of the final output data to aconstant data rate. For example, when a main service data rate is set to15 Mbps, and when a mobile service data rate is set to 1 Mbps, and whenthe output data rate of the service multiplexer 110 is required to bemaintained at 19.39 Mbps, the multiplexer 270 may insert null data or anull data packet to the final output data, thereby setting the finaloutput data rate to 19.39 Mbps. Herein, the null data may be generatedfrom the multiplexer 270 or generated from an external part.

The transmitter 120 receiving the null data should first remove the nulldata and then process the remaining data. Therefore, identificationinformation for identifying the null data is required by the transmitter120. A multiplexer for inserting the null data multiplexing andtransmitting the identification information along with the null datawill be given as an exemplary embodiment of the present invention.

For example, when the multiplexer 270 inserts null data, identificationinformation for identifying the null data is also multiplexed andtransmitted by the multiplexer 270. Herein, the identificationinformation may use a value pre-decided based upon an agreement betweenthe transmitting system and the receiving system, or the identificationinformation may be configured as a separate set of data. Alternatively,the identification information may also use a modified position value,the position value being predetermined in the null data packet.

For example, in the present invention, a synchronization byte valuewithin a header of a null data packet may be modified, so as to be usedas the identification information. Alternatively, atransport_error_indicator_flag may be set to ‘1’, so as to be used asthe identification information. Herein, any value that can identify thenull data may be used as the identification information. Therefore, thepresent invention is not limited only to the examples given in thedescription set forth herein.

Meanwhile, the main service ancillary data may include main serviceprogram specific information (PSI)/program and system informationprotocol (PSIP) information. Similarly, the mobile service ancillarydata may include mobile service PSI/PSIP information. Additionally,mobile service control data may also be included. And, in this case,information for controlling a transmission network may also be includedin the control data. Furthermore, when the multiplexer 270 multiplexesthe main service data packet and the mobile service data packet, themultiplexer 270 may include a packet identifier (PID) for identifyingeach of the main service data packet and the mobile service data packet,respectively. In another example, a bitwise inversion may be performedon a MPEG synchronization byte of the mobile service data packet, so asto identify the mobile service data packet from the main service datapacket.

FIG. 3 illustrates a block diagram of a transmitter according to thepresent invention. Referring to FIG. 3, the transmitter includes ademultiplexer (DEMUX) 301, a packet jitter mitigator 302, anpre-processor 303, and a first multiplexer 304. Additionally, thetransmitter also includes a data randomizer 305, a RSencoder/non-systematic RS encoder 306, a data interleaver 307, a parityreplacer 308, a non-systematic RS encoder 309, a trellis-encoding module310, a second multiplexer 311, a pilot inserter 312, a modulator 313,and a radio frequency (RF)-up converter 314.

FIG. 4 illustrates a block diagram of the pre-processor 303 according toan embodiment of the present invention. Herein, the pre-processor 303includes a data randomizer 401, a RS frame encoder 402, a blockprocessor 403, a group formatter 404, a data deinterleaver 405, and apacket formatter 406. In transmitter having the above-describedstructure, the demultiplexer 301 separates main service data and mobileservice data by demultiplexing the data transmitted from the servicemultiplexer. Then, the separated main service data are outputted to thepacket jitter mitigator 302, and the separated mobile service data areoutputted to the pre-processor 303.

At this point, when the service multiplexer 110 inserts null data inorder to match the data rate and transmits the processed data, thedemultiplexer 301 refers to identification information transmitted alongwith the processed data so as to discard the null data. Then, thedemultiplexer 301 demultiplexes only remaining data, which are thenoutput to each corresponding block. The pre-processor 303 performsadditional encoding so that the mobile service data can respond moreeffectively to noise and channel environment that undergoes frequentchanges. For this, the mobile service data separated by thedemultiplexer 301 are output to the data randomizer 401 of thepre-processor 303.

The data randomizer 401 receives mobile service data and randomizes thereceived data, thereby outputting the processed mobile service data tothe RS frame encoder 402. At this point, by having the data randomizer401 randomize the mobile service data, a later randomizing process onthe mobile service data performed by a data randomizer 305, which ispositioned in a later block, may be omitted. The randomizer of theconventional system may be identically used as the randomizer forrandomizing the mobile service data. Alternatively, any other type ofrandomizer may also be used for this process.

The RS frame encoder 402 performs at least one of an error correctionencoding process and an error detection encoding process on the inputtedrandomized mobile service data so as to provide robustness on thecorresponding mobile service data. Thus, by providing robustness on themobile service data, a group error that may occur due to a change in thefrequency environment can be scattered, thereby enabling thecorresponding data to respond to the severely vulnerable and frequentlychanging frequency environment. The RS frame encoder 402 may alsoinclude a row permutation process, which permutes mobile service datahaving a predetermined size in row units. Herein, RS encoding is appliedas the error correction encoding process, and cyclic redundancy check(CRC) encoding is applied as the error detection encoding process. Whenperforming RS encoding, parity data that are to be used for errorcorrection are generated. And, when performing CRC encoding, CRC datathat are to be used for error detection are generated.

In this embodiment of the present invention, the RS encoding will beadopting a forward error correction (FEC) method. The FEC corresponds toa technique for compensating errors that occur during the transmissionprocess. The CRC data generated by CRC encoding may be used forindicating whether or not the mobile service data have been damaged bythe errors while being transmitted through the channel. In the presentinvention, a variety of error detection coding methods other than theCRC encoding method may be used, or the error correction coding methodmay be used to enhance the overall error correction ability of thereceiving system.

As described above, the mobile service data encoded by the RS frameencoder 402 are inputted to the block processor 403. The block processor403 then encodes the inputted mobile service data at a coding rate ofG/H (wherein, G is smaller than H (i.e., G<H)) and then outputted to thegroup formatter 404. More specifically, the block processor 113 dividesthe mobile service data being inputted in byte units into bit units.Then, the G number of bits is encoded to H number of bits. Thereafter,the encoded bits are converted back to byte units and then outputted.For example, if 1 bit of the input data is coded to 2 bits andoutputted, then G is equal to 1 and H is equal to 2 (i.e., G=1 and H=2).Alternatively, if 1 bit of the input data is coded to 4 bits andoutputted, then G is equal to 1 and H is equal to 4 (i.e., G=1 and H=4).Hereinafter, the former coding rate will be referred to as a coding rateof 1/2 (1/2-rate coding), and the latter coding rate will be referred toas a coding rate of 1/4 (1/4-rate coding), for simplicity.

Herein, when using the 1/4 coding rate, the coding efficiency is greaterthan when using the 1/2 coding rate, and may, therefore, provide greaterand enhanced error correction ability. For such reason, when it isassumed that the data encoded at a 1/4 coding rate in the groupformatter 404, which is located near the end portion of the system, areallocated to a region in which the receiving performance may bedeteriorated, and that the data encoded at a 1/2 coding rate areallocated to a region having excellent receiving performance, thedifference in performance may be reduced. At this point, the blockprocessor 403 may also receive additional information data, such assignaling information including system information. Herein, theadditional information data may also be processed with either 1/2-ratecoding or 1/4-rate coding as in the step of processing the enhance data.Thereafter, additional information data, such as signaling information,is also considered the same as the mobile service data and processedaccordingly. The signaling information is information required that areceiving system receives and processes data included in a data group.The signaling information may include data group information,multiplexing information, burst information, and so on.

Meanwhile, the group formatter 404 inserts mobile service data that areoutputted from the block processor 403 in corresponding regions within adata group, which is configured in accordance with a pre-defined rule.Also, with respect to the data deinterleaving process, each place holderor known data are also inserted in corresponding regions within the datagroup. At this point, the data group may be divided into at least onehierarchical region. Herein, the type of mobile service data beinginserted to each region may vary depending upon the characteristics ofeach hierarchical region. For example, each region may be divided basedupon the receiving performance within the data group.

Herein, the data group is divided into a plurality of different regionsso that each region can be used for different purposes. Morespecifically, a region having less or no interference from the mainservice data may provide a more enhanced (or powerful) receivingperformance as compared to a region having relatively more interferencefrom the main service data. Furthermore, when using a system insertingand transmitting known data into the data group, and when a long knowndata sequence is to be consecutively inserted into the mobile servicedata, a known data sequence having a predetermined length may beconsecutively inserted into a region having no interference from themain service data. Conversely, in case of the regions havinginterference from the main service data, it is difficult toconsecutively insert long known data sequences and to periodicallyinsert the known data into the corresponding regions due to theinterference from the main service data.

In addition, the group formatter 404 also inserts supplemental (orancillary) data, such as signaling information that notifies the overalltransmission information, other than the mobile service data in the datagroup. Also, apart from the encoded mobile service data outputted fromthe block processor 403, the group formatter 404 also inserts MPEGheader place holders, non-systematic RS parity place holders, mainservice data place holders, which are related to data deinterleaving ina later process. Herein, the main service data place holders areinserted because the mobile service data bytes and the main service databytes are alternately mixed with one another based upon the input of thedata deinterleaver. For example, based upon the data outputted after thedata-deinterleaving process, the place holder for the MPEG header may beallocated at the very beginning of each packet.

Furthermore, the group formatter 404 either inserts known data generatedin accordance with a pre-determined method or inserts known data placeholders for inserting the known data in a later process. Additionally,place holders for initializing the trellis encoding module 310 are alsoinserted in the corresponding regions. For example, the initializationdata place holders may be inserted in the beginning of the known datasequence. Herein, the size of the mobile service data that can beinserted in a data group may vary in accordance with the sizes of thetrellis initialization data or known data, MPEG headers, and RS paritydata.

The output of the group formatter 404 is inputted to the datadeinterleaver 405. And, the data deinterleaver 405 deinterleaves data byperforming an inverse process of the data interleaver on the data andplace holders within the data group, which are then outputted to thepacket formatter 406. The packet formatter 406 removes the main servicedata place holders and the RS parity place holders that were allocatedfor the deinterleaving process from the deinterleaved data beinginputted. Then, the packet formatter 406 groups the remaining portionand replaces the 4-byte MPEG header place holder with an MPEG. Also,when the group formatter 404 inserts known data place holders, thepacket formatter 406 may insert actual known data in the known dataplace holders, or may directly output the known data place holderswithout any modification in order to make replacement insertion in alater process. Thereafter, the packet formatter 406 identifies the datawithin the packet-formatted data group, as described above, as a188-byte unit mobile service data packet (i.e., MPEG TS packet), whichis then provided to the first multiplexer 304.

The first multiplexer 304 multiplexes the mobile service data packet ofthe 188-byte unit outputted from the packet formatter 406 and the mainservice data packet in accordance with a pre-defined multiplexingmethod. Then, the first multiplexer 304 outputs the multiplexed datapackets to the data randomizer 305. Herein, the multiplexing method mayvary in accordance with various variables of the system design. One ofthe multiplexing methods of the first multiplexer 304 consists ofproviding a burst-on section and burst-off section along a time axis, asshown in FIG. 5( a), and, then, transmitting a plurality of data groupsduring a burst-on section and transmitting only the main service dataduring the burst-off section. At this point, main service data may alsobe transmitted in the burst-on section. More specifically, as shown inFIG. 5( b), a plurality of consecutive mobile service data packets aregrouped to form a data group. And, a plurality of such data groups ismixed with main service data packets so as to create a burst-on section.

In this case, mobile service data and main service data co-exist in aburst-on section, as shown in FIG. 5( a), and only the main service dataexist in the burst-off section. Therefore, the main service data sectiontransmitting the main service data exist in both the burst-on sectionand the burst-off section. At this point, the number of main servicedata packets included in the main service data section within theburst-on section and the number of main service data packets included inthe main service data section within the burst-off section may be equalto or different from one another. When the mobile service data aretransmitted in burst units, as described above, a receiving system thatonly receives the mobile service data may turn on the power only duringthe burst-on section so as to receive the corresponding data. Also, inthis case, the receiving system may turn off the power during burst-offsection, thereby preventing the main service data from being received.Thus, the receiving system is capable of reducing excessive powerconsumption.

However, since a data group including mobile service data in-between thedata bytes of the main service data during the packet multiplexingprocess, the shifting of the chronological position (or place) of themain service data packet becomes relative. Also, a system object decoder(i.e., MPEG decoder) for processing the main service data of the digitalbroadcast receiving system, receives and decodes only the main servicedata and recognizes the mobile service data packet as a null datapacket. Therefore, when the system object decoder of the receivingsystem receives a data group including mobile service data and a mainservice data packet that is multiplexed with the data group, a packetjitter occurs.

At this point, since a multiple-level buffer for the video data existsin the system object decoder and the size of the buffer is relativelylarge, the packet jitter generated from the first multiplexer 304 doesnot cause any serious problem in case of the video data. However, sincethe size of the buffer for the audio data is relatively small, thepacket jitter may cause considerable problem. More specifically, due tothe packet jitter, an overflow or underflow may occur in the buffer forthe main service data of the receiving system (e.g., the buffer for theaudio data). Therefore, the packet jitter mitigator 302 re-adjusts therelative position of the main service data packet so that the overflowor underflow does not occur in the system object decoder.

In the present invention, examples of repositioning places for the audiodata packets within the main service data in order to minimize theinfluence on the operations of the audio buffer will be described indetail. FIG. 5( c) illustrates, in TS packet units, a main service datasection within the burst-on section that is being inputted to the packetjitter mitigator 302 of the transmitter. The packet jitter mitigator 302repositions audio packets of the main service data section, as shown inFIG. 5( d), so that the audio data packets of the main service can bepositioned as equally and uniformly as possible. The standard forrepositioning the audio data packets in the main service data performedby the packet jitter mitigator 302 will now be described. Herein, it isassumed that the packet jitter mitigator 302 knows the same multiplexinginformation as that of the first multiplexer 304, which is placedfurther behind the packet jitter mitigator 302.

Firstly, if one audio data packet exists in the main service datasection (e.g., the main service data section positioned between two datagroups) within the burst-on section, the audio data packet is positionedat the very beginning of the main service data section. Alternatively,if two audio data packets exist in the corresponding data section, oneaudio data packet is positioned at the very beginning and the otheraudio data packet is positioned at the very end of the main service datasection. Further, if more than three audio data packets exist, one audiodata packet is positioned at the very beginning of the main service datasection, another is positioned at the very end of the main service datasection, and the remaining audio data packets are positioned between thefirst and last audio data packets at equal intervals (as shown in FIG.5( c) and FIG. 5( d)).

Secondly, during the main service data section within the burst-offsection, which is placed immediately before the beginning of a burst-onsection (i.e., during a burst-off section), the audio data packet isplaced at the very end of the main service data section. Thirdly, duringa main service data section within the burst-off section subsequent tothe burst-on section, the audio data packet is positioned at the verybeginning of the main service data section. And, finally, the datapackets other than audio data packets are positioned in accordance withthe inputted order in vacant spaces (i.e., spaces that are notdesignated for the audio data packets). Meanwhile, when the positions ofthe main service data packets are relatively re-adjusted, associatedprogram clock reference (PCR) values may also be modified accordingly.The PCR value corresponds to a time reference value for synchronizingthe time of the system target decoder. Herein, the PCR value is insertedin a specific region of a TS packet and then transmitted.

In the example of the present invention, the packet jitter mitigator 302also performs the operation of modifying the PCR value. The output ofthe packet jitter mitigator 302 is inputted to the first multiplexer304. As described above, the first multiplexer 304 multiplexes the mainservice data packet outputted from the packet jitter mitigator 302 withthe mobile service data packet outputted from the pre-processor 303 intoa burst structure in accordance with a pre-determined multiplexing rule.Then, the first multiplexer 304 outputs the multiplexed data packets tothe data randomizer 305.

If the inputted data correspond to the main service data packet, thedata randomizer 305 performs the same randomizing process as that of theconventional randomizer. More specifically, the synchronization bytewithin the main service data packet is deleted. Then, the remaining 187data bytes are randomized by using a pseudo random byte generated fromthe data randomizer 305. Thereafter, the randomized data are outputtedto the RS encoder/non-systematic RS encoder 306.

On the other hand, if the inputted data correspond to the mobile servicedata packet, the data randomizer 305 deletes the synchronization bytefrom the 4-byte MPEG header included in the mobile service data packetand, then, performs the randomizing process only on the remaining 3 databytes of the MPEG header. Thereafter, the randomized data bytes areoutputted to the RS encoder/non-systematic RS encoder 306. Additionally,the randomizing process is not performed on the remaining portion of themobile service data excluding the MPEG header. In other words, theremaining portion of the mobile service data packet is directlyoutputted to the RS encoder/non-systematic RS encoder 306 without beingrandomized. This is because a randomizing process has already beenperformed on the mobile service data in the data randomizer 401. Also,the data randomizer 305 may or may not perform a randomizing process onthe known data (or known data place holders) and the initialization dataplace holders included in the mobile service data packet.

The RS encoder/non-systematic RS encoder 306 performs an RS encodingprocess on the data being randomized by the data randomizer 305 or onthe data bypassing the data randomizer 305, so as to add 20 bytes of RSparity data. Thereafter, the processed data are outputted to the datainterleaver 307. Herein, if the inputted data correspond to the mainservice data packet, the RS encoder/non-systematic RS encoder 306performs the same systematic RS encoding process as that of theconventional system, thereby adding the 20-byte RS parity data at theend of the 187-byte data. Alternatively, if the inputted data correspondto the mobile service data packet, the RS encoder/non-systematic RSencoder 306 performs a non-systematic RS encoding process. At thispoint, the 20-byte RS parity data obtained from the non-systematic RSencoding process are inserted in a pre-decided parity byte place withinthe mobile service data packet.

The data interleaver 307 corresponds to a byte unit convolutionalinterleaver. The output of the data interleaver 307 is inputted to theparity replacer 308 and to the non-systematic RS encoder 309. Meanwhile,a process of initializing a memory within the trellis encoding module310 is primarily required in order to decide the output data of thetrellis encoding module 310, which is located after the parity replacer308, as the known data pre-defined according to an agreement between thereceiving system and the transmitting system. More specifically, thememory of the trellis encoding module 310 should first be initializedbefore the received known data sequence is trellis-encoded.

At this point, the beginning portion of the known data sequence that isreceived corresponds to the initialization data place holder and not tothe actual known data. Herein, the initialization data place holder hasbeen included in the data by the group formatter 404 in an earlierprocess. Therefore, the process of generating initialization data andreplacing the initialization data place holder of the correspondingmemory with the generated initialization data are required to beperformed immediately before the inputted known data sequence istrellis-encoded.

Additionally, a value of the trellis memory initialization data isdecided and generated based upon a memory status of the trellis encodingmodule 310. Further, due to the newly replaced initialization data, aprocess of newly calculating the RS parity and replacing the RS parity,which is outputted from the data interleaver 307, with the newlycalculated RS parity is required. Therefore, the non-systematic RSencoder 309 receives the mobile service data packet including theinitialization data place holders, which are to be replaced with theactual initialization data, from the data interleaver 307 and alsoreceives the initialization data from the trellis encoding module 310.

Among the inputted mobile service data packet, the initialization dataplace holders are replaced with the initialization data, and the RSparity data that are added to the mobile service data packet.Thereafter, a new non-systematic RS parity is calculated and thenoutputted to the parity replacer 308. Accordingly, the parity replacer308 selects the output of the data interleaver 307 as the data withinthe mobile service data packet, and the parity replacer 308 selects theoutput of the non-systematic RS encoder 309 as the RS parity data. Then,the selected data are outputted to the trellis encoding module 310.

Meanwhile, if the main service data packet is inputted or if the mobileservice data packet, which does not include any initialization dataplace holders that are to be replaced, is inputted, the parity replacer308 selects the data and RS parity that are outputted from the datainterleaver 307. Then, the parity replacer 308 directly outputs theselected data to the trellis encoding module 310 without anymodification. The trellis encoding module 310 converts the byte-unitdata to symbol units and performs a 12-way interleaving process so as totrellis-encode the received data. Thereafter, the processed data areoutputted to the second multiplexer 311.

The second multiplexer 311 inserts a field synchronization signal and asegment synchronization signal to the data outputted from the trellisencoding module 310 and, then, outputs the processed data to the pilotinserter 312. Herein, the data having a pilot inserted by the pilotinserter 312 are modulated by the modulator 313 in accordance with apre-decided modulating method. Thereafter, the modulated data aretransmitted to each receiving system through the radio frequency (RF)up-converter 314.

FIG. 6 illustrates a block diagram showing a structure of a receivingsystem according to the present invention. The receiving system of FIG.6 uses known data information, which is inserted in the mobile servicedata section and, then, transmitted by the transmitting system, so as toperform carrier synchronization recovery, frame synchronizationrecovery, and channel equalization, thereby enhancing the receivingperformance. Referring to FIG. 6, the receiving system includes a tuner601, a demodulator 602, an equalizer 603, a known sequence detector 604,a block decoder 605, a data deformatter 606, a RS frame decoder 607, adata derandomizer 608, a data deinterleaver 609, a RS decoder 610, and adata derandomizer 611. Herein, for simplicity of the description of thepresent invention, the data deformatter 606, the RS frame decoder 607,and the data derandomizer 608 will be collectively referred to as amobile service data processing unit. And, the data deinterleaver 609,the RS decoder 610, and the data derandomizer 611 will be collectivelyreferred to as a main service data processing unit.

More specifically, the tuner 601 tunes a frequency of a particularchannel and down-converts the tuned frequency to an intermediatefrequency (IF) signal. Then, the tuner 601 outputs the down-converted IFsignal to the demodulator 602 and the known sequence detector 604. Thedemodulator 602 performs self gain control, carrier recovery, and timingrecovery processes on the inputted passband IF signal, thereby modifyingthe IF signal to a baseband signal. Then, the demodulator 602 outputsthe newly created baseband signal to the equalizer 603 and the knownsequence detector 604. The equalizer 603 compensates the distortion ofthe channel included in the demodulated signal and then outputs theerror-compensated signal to the block decoder 605.

At this point, the known sequence detector 604 detects the knownsequence place inserted by the transmitting end from the input/outputdata of the demodulator 602 (i.e., the data prior to the demodulationprocess or the data after the demodulation process). Thereafter, theplace information along with the symbol sequence of the known data,which are generated from the detected place, is outputted to thedemodulator 602 and the equalizer 603. Also, the known sequence detector604 outputs a set of information to the block decoder 605. This set ofinformation is used to allow the block decoder 605 of the receivingsystem to identify the mobile service data that are processed withadditional encoding from the transmitting system and the main servicedata that are not processed with additional encoding. In addition,although the connection status is not shown in FIG. 6, the informationdetected from the known sequence detector 604 may be used throughout theentire receiving system and may also be used in the data deformatter 606and the RS frame decoder 607. The demodulator 602 uses the known datasymbol sequence during the timing and/or carrier recovery, therebyenhancing the demodulating performance. Similarly, the equalizer 603uses the known data so as to enhance the equalizing performance.Moreover, the decoding result of the block decoder 605 may be fed-backto the equalizer 603, thereby enhancing the equalizing performance.

Meanwhile, if the data being inputted to the block decoder 605, afterbeing channel-equalized by the equalizer 603, correspond to the mobileservice data having additional encoding and trellis encoding performedthereon by the transmitting system, trellis decoding and additionaldecoding processes are performed on the inputted data as inverseprocesses of the transmitting system. Alternatively, if the data beinginputted to the block decoder 605 correspond to the main service datahaving only trellis encoding performed thereon, and not the additionalencoding, only the trellis decoding process is performed on the inputteddata as the inverse process of the transmitting system. The data groupdecoded by the block decoder 605 is outputted to the data deformatter606, and the main service data are outputted to the data deinterleaver609.

More specifically, if the inputted data correspond to the main servicedata, the block decoder 605 performs Viterbi decoding on the inputteddata so as to output a hard decision value or to perform a hard-decisionon a soft decision value, thereby outputting the result. Meanwhile, ifthe inputted data correspond to the mobile service data, the blockdecoder 605 outputs a hard decision value or a soft decision value withrespect to the inputted mobile service data. In other words, if theinputted data correspond to the mobile service data, the block decoder605 performs a decoding process on the data encoded by the blockprocessor and trellis encoding module of the transmitting system.

At this point, the RS frame encoder of the pre-processor included in thetransmitting system may be viewed as an external code. And, the blockprocessor and the trellis encoder may be viewed as an internal code. Inorder to maximize the performance of the external code when decodingsuch concatenated codes, the decoder of the internal code should outputa soft decision value. Therefore, the block decoder 605 may output ahard decision value on the mobile service data. However, when required,it may be more preferable for the block decoder 605 to output a softdecision value.

Meanwhile, the data deinterleaver 609, the RS decoder 610, and the dataderandomizer 611 are blocks required for receiving the main servicedata. Therefore, the above-mentioned blocks may be omitted from thestructure of a receiving system that only receives the mobile servicedata. The data deinterleaver 609 performs an inverse process of the datainterleaver included in the transmitting system. In other words, thedata deinterleaver 609 deinterleaves the main service data outputtedfrom the block decoder 605 and outputs the deinterleaved main servicedata to the RS decoder 610.

The RS decoder 610 performs a systematic RS decoding process on thedeinterleaved data and outputs the processed data to the dataderandomizer 611. The data derandomizer 611 receives the output of theRS decoder 610 and generates a pseudo random data byte identical to thatof the randomizer included in the transmitting system. Thereafter, thedata derandomizer 611 performs a bitwise exclusive OR (XOR) operation onthe generated pseudo random data byte, thereby inserting the MPEGsynchronization bytes to the beginning of each packet so as to outputthe data in 188-byte main service data packet units.

Meanwhile, the data being outputted from the block decoder 605 to thedata deformatter 606 are inputted in the form of a data group. At thispoint, the data deformatter 606 already knows the structure of the datathat are to be inputted and is, therefore, capable of identifying thesignaling information, which includes the system information, and themobile service data from the data group. Thereafter, the datadeformatter 606 outputs the identified signaling information to a blockfor processing signaling information (not shown) and outputs theidentified mobile service data to the RS frame decoder 607. At thispoint, the data deformatter 606 removes the known data, trellisinitialization data, and MPEG header, which were inserted in the mainservice data and data group, and also removes the RS parity, which wasadded by the RS encoder/non-systematic RS encoder or non-systematic RSencoder of the transmitting system, from the corresponding data.Thereafter, the processed data are outputted to the RS frame decoder607. More specifically, the RS frame decoder 607 receives only the RSencoded and/or CRC encoded mobile service data that are transmitted fromthe data deformatter 606.

The RS frame decoder 607 performs an inverse process of the RS frameencoder included in the transmitting system so as to correct the errorwithin the RS frame. Then, the RS frame decoder 607 adds the 1-byte MPEGsynchronization service data packet, which had been removed during theRS frame encoding process, to the error-corrected mobile service datapacket. Thereafter, the processed data packet is outputted to the dataderandomizer 608. The data derandomizer 608 performs a derandomizingprocess, which corresponds to the inverse process of the randomizerincluded in the transmitting system, on the received mobile servicedata. Thereafter, the derandomized data are outputted, thereby obtainingthe mobile service data transmitted from the transmitting system.

As described above, the present invention has the following advantages.More specifically, the present invention is robust against (or resistantto) any error that may occur when transmitting mobile service datathrough a channel. And, the present invention is also highly compatibleto the conventional system. Moreover, the present invention may alsoreceive the mobile service data without any error even in channelshaving severe ghost effect and noise.

Additionally, by performing error correction encoding and errordetection encoding processes on the mobile service data and transmittingthe processed data, the present invention may provide robustness to themobile service data, thereby enabling the data to effectively respond tothe frequent change in channels. Also, when the present inventionmultiplexes the main service data and the mobile service data in a burststructure, a relative position of a main service data packet isre-adjusted and then multiplexed, thereby mitigating packet jitter,which may occur when the receiving system receives the multiplexed mainservice data packet.

Furthermore, the present invention is even more effective when appliedto mobile and portable receivers, which are also liable to a frequentchange in channel and which require protection (or resistance) againstintense noise.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method of processing a broadcast signal in abroadcast transmitter, the method comprising: identifying a null datapacket included in an input stream that includes the null data packetand a first broadcast data packet for a first service; deleting theidentified null data packet in the input stream; randomizing firstbroadcast data of the first broadcast data packet in the input stream inwhich the null data packet is deleted; first encoding the randomizedfirst broadcast data systematically; interleaving the first-encodedfirst broadcast data; and transmitting the broadcast signal includingthe interleaved first broadcast data, wherein the broadcast signalfurther includes second broadcast data for a second service multiplexedwith the first broadcast data and information for identifying the firstbroadcast data and the second broadcast data, and wherein the firstbroadcast data and the second broadcast data have a different robustnesslevel.
 2. The method of claim 1, wherein the first broadcast data arerandomized after a sync byte in the first broadcast data packetincluding the first broadcast data is removed.
 3. The method of claim 1,further comprising: second encoding the interleaved first broadcastdata.
 4. The method of claim 1, wherein the null data packet is includedin the input stream in order to accommodate variable data rate servicesin the input stream having a constant bit rate.
 5. A broadcasttransmitter for processing a broadcast signal, the broadcast transmittercomprising: an input processor for identifying a null data packetincluded in an input stream that includes the null data packet and afirst broadcast data packet for a first service, and deleting theidentified null data packet in the input stream; a randomizer forrandomizing first broadcast data of the first broadcast data packet inthe input stream in which the null data packet is deleted; a firstencoder for first encoding the randomized first broadcast datasystematically; an interleaver for interleaving the first-encoded firstbroadcast data; and a transmitting unit for transmitting the broadcastsignal including the interleaved first broadcast data, wherein thebroadcast signal further includes second broadcast data for a secondservice multiplexed with the first broadcast data and information foridentifying the first broadcast data and the second broadcast data, andwherein the first broadcast data and the second broadcast data have adifferent robustness level.
 6. The broadcast transmitter of claim 5,wherein the first broadcast data are randomized after a sync byte in thefirst broadcast data packet including the first broadcast data isremoved.
 7. The broadcast transmitter of claim 5, further comprising: asecond encoder for second encoding the interleaved first broadcast data.8. The broadcast transmitter of claim 5, wherein the null data packet isincluded in the input stream in order to accommodate variable data rateservices in the input stream having a constant bit rate.